Transcriptomic analysis of Manila clam Ruditapes philippinarum under lipopolysaccharide challenge provides molecular insights into immune response.

The Manila clam, Ruditapes philippinarum, is an economically important shellfish in marine aquaculture. A better understanding of the immune system in R. philippinarum will provide the basis for the development of strategies to mitigate the impact of infectious diseases affecting this species but can also be of relevance for other bivalves of commercial interest. In this study, the transcriptional response of the Manila clam under lipopolysaccharide (LPS) challenge was characterized using RNA sequencing. The transcriptomes of LPS challenged group of clams (LH1, LH2 and LH3), and the PBS control group (CH1, CH2 and CH3), were sequenced with the Illumina HiSeq platform. Compared with the unigene expression profile of the control group, 223 unigenes were up-regulated and 389 unigenes were down-regulated in the LPS challenged group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that signal transduction, defense response, and immune-related pathways such as Chemokine signaling pathway, Complement and coagulation cascades, NOD-like receptor signaling pathway, and Inflammatory mediator regulation of TRP channels in sensory system were the most highly enriched pathways among the genes that were differentially expressed under LPS challenge. This study present understanding of the molecular basis underpinning response to LPS challenge and provides useful information for future work on the molecular mechanism of pathogen resistance and immunity in Manila clam.

Physiological and biochemical responses of Dosinia corrugata to different thermal and salinity stressors.

Temperature and salinity are major factors affecting geographic distribution, reproduction, and physiological processes of marine and estuarine organisms. In this study, the effects of different temperatures and salinity on the respiratory metabolism and physiological response were evaluated in D. corrugata by measuring oxygen consumption rate (OCR), ammonia excretion rate (AER), and glycolytic enzyme activity. An increase in the OCR of D. corrugata with increasing temperature was observed. No peak of oxygen consumption was observed in D. corrugata over the temperature range evaluated. There was an increase in AERs with increasing temperature and salinity, respectively. With increasing salinity, the enzyme activity increased until it reached a peak at a salinity of 30 ppt, while the highest HK and LDH activity was observed at a salinity of 25 ppt. Our results may be used to optimize the temperature and salinity conditions for optimal growth and survival of D. corrugata and to provide basic information for conservation management and fishing moratorium of this economically important bivalve species. The enzyme activity decreased slightly from 15 to 20°C, but when the temperature exceeded 20°C, enzyme activity increased, reaching a maximum at 30°C (tested range of 10-30°C). With increasing salinity, the enzyme activity increased until it reached a peak at a salinity of 30 ppt, but once the salinity was greater than 30 ppt, the enzyme activity began to decrease up to salinity of 35 ppt.